Stranded… could use some ideas.

[7900_Blazer]

@7900_Blazer You have already gotten some great responses but I'll give mine. I'm going to go though your questions one by one, and I'll put my answers in italics.

I few questions/thoughts from this experience:

- At operating temp, my engine coolant is roughly 210 degrees... won't gas with ethanol simple turn to vapor at that temp - requiring moving from a mechanical pump to an electric pump?

No, first of all that's coolant temp and you want the fuel to vaporize as it enters the combustion chamber anyway. I recently drove my square in 110F with a load uphill, down hill on the highway and in traffic, about 100 miles in all. I'm running a mechanical pump with factory return and it never once even tried to vapor lock nor did it act any different from any other day. The only way you'll know for sure is to check the temp of the fuel pump and lines with an IR temp gun, you can get one for like $20 at harbor freight and it'll save you from guessing. Anything below 220 coolant temp is considered normal, and often in traffic the fan clutch won't keep it much below 210 - 220F

- I'm NOT excited about relying on an Edelbrock electric fuel pump: one with many reviewers having experienced their lack of build quality/reliability - are there better 'carbureted' electronic fuel pumps you all use?

At the shop I strongly discourage everyone from going to electric fuel pumps unless they have a good reason like on a carbureted vortec motor. I don't think there is any electric pump, with the exception of modern FI cars, that can even remotely compete with a mechanical pump in terms of reliability.

- I was convinced the pop-tart wrapper was the problem... but learned differently when my Blazer got up to operating temperature (and I was again on the side of the road)

Good to know, but I'd still encourage you to do a temp check on the lines / pump. Also it is not hard to add a return line to a non-return system, or to verify that the return system is functional if it has one in order to keep the mechanical pump.

- Am I left with the fact that all 'modern' (ethanol) fuel has a lower boiling point (turning from liquid to vapor), so having a pump NOT bolted to the side of the motor is the new normal?

No, as I said earlier I'm still rockin a mechanical pump, as are many others. I'd say switching to electrical is uncommon just for vapor locking in an otherwise mostly stock setup. Keep in mind while you are talking about gasoline it's not just ethanol and gas mixed up, it's complex compounds and additives. I have heard it said that gas boils easier than it use to but it's all word of mouth and I've seen zero proof of that. Also only 10% of pump gas is ethanol. Think about it, it's 90% the gas. I don't think that ethanol is to blame. Prove it by filling up at an ethanol free station, often found at farm supply stations as well as others.

- Is there a realistic option to get the operating temperature of my motor down to say 180, and with minimal pressure, never see a vapor lock issue?

You can install a cooler thermostat, if it's got a 195 go 180, if it's got a 180 go 160, but again it has more to do with exhaust temps, which is right next to the pump and lines. I just went rounds with a guy that has a 55 bel air, he had a 195 stat and was getting some mild vapor locking. One of his friends told him a lower temp t-stat would fix it and he wanted a 160, I told him it would not fix his vapor locking, and it didn't. What did fix it was shortening up the rubber line from the frame to the pump. Someone had replaced them in the past used way to much rubber hose and loop it towards the exhaust manifold. I'm not saying there isn't a chance cooler temp T-stat won't help, I'm just saying I haven't seen it help.... Ever.

- I don't understand why I've never had this happen in Texas...

could be the gas. There are lots of additives in gas we have just made a big deal out of the ethanol. Remember lead how about MMT, both were well known additives blended in. There are also additives blended into the mix to increase the boiling point, and they maybe different from place to place and season to season. Also as you said a lot more big hills, you step on the gas hold it there and those manifolds may get hotter then when your cruising in Texas.

- I don't understand why in Colorado Springs, running off the gas can in the floorboard got me going again...

The wrapper in the tank maybe? Maybe it's not vapor lock. We have all through out other ideas so I won't rehash.

- If you say 'the gas coming from the gas can in the floorboard was cooler than the pre-heated gas running through the factory lines down the frame'.. my response would be: 'then why did it still vapor lock when I ran a new rubber line outside the frame rail away from the heat? - I would add that the mechanical fuel pump was the same temperature as the block... so any fuel entering it would turn to vapor..

Seems to me this makes it even less likely to be vapor lock, but vapor locking can be tricky sometimes. Black rubber line is good at absorbing heat so if it was close to the exhaust manifold before you got it to the outside of the frame rail, or for some reason that manifold is getting hot than it should be, but then we'd circle back around to why did it not with the can on the floor. Was this before or after the wrapper was found?

- My wife's GMC Yukon has 360k... and she'd driving it around the mountains like it's brand new... I've tried to upgrade it for her but she won't budge until she hits 400k.... never touched the electronic fuel pump inside the tank... so how do I replicate that reliability? - Go to EFI?

Fix the current problem and move on when or if you nail it down without modifying the factory system we'll all go ah, so that was it! Yes you could go EFI that would solve it but how much you want to spend on a good EFI system? a couple grand, more maybe?!

-To say the least, I'm pretty bummed about the future prospects of just running an old stock Chevy...

It sucks right now I know, I've been there. I was 1,000 miles away from home and punched a 2 foot hole in the gas tank of an Oldsmobile I use to own. Brought it home with a rented truck and trailer, adding that, missed work and cost to repair I was in it way more than the car was worth, and at the time I thought I should have left it in California and driven a rental home, it would have been cheaper. But in the end I enjoyed many more trips in that car. Or the time I was across the country and had reverse go out in another rig. Most of us could probably share breakdown horror stories. The most important thing is to be as prepared as possible, no matter the age of the vehicle keep maintenance up to date, and know that driving a new to you used vehicle of any age could hold weaknesses you don't know about yet. Even still issues occur. Roll with it as best you can and enjoy the rest of your trip, next time you'll have these issues ironed out!

Thank you for the detailed responses.

I think my first upgrade will be adding a return line. The only question I have is what is best option for adding a return to the tank.

 

[7900_Blazer]

That's exactly what I would do. You can get a new 4-port sending unit also to make sure you have the correct parts all the way through.

Basically a 2-port pump has an internal relief valve that allows all the fuel not necessary to keep 7-psi of pressure in the line to "bypass" the pump. In the 2-port version it just stops flowing internally(which allows it to get MUCH hotter). In the three port version, the pump pushes a full pulse every time and an internal spring allows 7-psi to go to the carb and bypasses all of the remaining fuel through the return line. This keeps a constant flow of fuel running through the feed, pump, and return lines to help keep it cool.

I got a new fuel pump for mine a few years ago when I first got my truck going, since it had sat for over 10 years. I transferred it over to my new motor last weekend when I was firing it up on the stand and just noticed it is weeping fuel and/or oil from the crimp. I'm not sure if it is the pump going bad or if it had some junk that worked its way in there from a leaky engine bay over the years. It's kind of a pain to change the pump once it's in the engine bay though, so I'm going to just replace it before I stick the new motor in. Cheap insurance.

I changed the mechanical pump on this Blazer in the parking lot of Oreilly’s in Pueblo… the only real pain was keeping the pump rod up to slide in the pump lever…

 

[7900_Blazer]

Quick question: my oem sending unit has three ports:
- a supply tube to the fuel pump
- a vent tube up to the gas cap
- a vent that has basically a dust cover on it.

Can I connect a return line to either of the vent tubes or are the internally ’one-way’ vents?

In other words, can I use my existing sending unit to add a return line or must I upgrade to a 4 port sending unit?

 

[7900_Blazer]

The boiling point temperature relies heavily on pressure. The temperature required for a state change decreases as the pressure decreases. This is the same principal used in your AC system and engine cooling system as well. Its why your coolant system is pressurized to 10-12psi, to increase the boiling point. You also have to understand that a state change absorbs a huge amount of energy and thermal transfer is not instantaneous. The real solution to vapor lock is to add a return line. Your wifes tahoe is fuel injected and has the pump submerged in the fuel tank. This means that the pump is cooled by the fuel in the tank and that all of the fuel in the entire fuel line is pressurized to about 56psi, which raises the boiling point to a very high temperature.

A carbureted engine has the pump on the motor, which means that it is pulling a vacuum in the hose(lowering the pressure and therefore lowering the boiling point) every time it pumps. At a higher elevation, the ambient air pressure is also lower, and therefore the boiling point starts out lower to begin with. The boiling point of water at the elevation of Colorado springs is almost 10 degrees cooler than it is at sea level.

Adding a return line allows excess fuel that is not needed to keep the carburetor filled to be cycled back to the fuel tank and will actually allow THAT fuel to vaporize first and actually help cool the pump down a lot. I would personally recommend putting in a three port pump and run the return line back to the tank first. You will likely not have another issue with it. I have a three port pump and have run my truck through the cascades at 3-5,000ft elevation and near 100 degrees with no issue. I had a 74 C20 for a while that would have the same symptoms you are having on hot days. It did not have a return line and I'm pretty sure it was vapor locking when I would get it on the freeway.

@Bextreme04 is there an option for the return line into the tank other than ordering a new sending unit? I ask because I can switch out the fuel pump and add a return line here in the mountains... but can order and replace a new sending unit here.

Thoughts?

 

[7900_Blazer]

The boiling point temperature relies heavily on pressure. The temperature required for a state change decreases as the pressure decreases. This is the same principal used in your AC system and engine cooling system as well. Its why your coolant system is pressurized to 10-12psi, to increase the boiling point. You also have to understand that a state change absorbs a huge amount of energy and thermal transfer is not instantaneous. The real solution to vapor lock is to add a return line. Your wifes tahoe is fuel injected and has the pump submerged in the fuel tank. This means that the pump is cooled by the fuel in the tank and that all of the fuel in the entire fuel line is pressurized to about 56psi, which raises the boiling point to a very high temperature.

A carbureted engine has the pump on the motor, which means that it is pulling a vacuum in the hose(lowering the pressure and therefore lowering the boiling point) every time it pumps. At a higher elevation, the ambient air pressure is also lower, and therefore the boiling point starts out lower to begin with. The boiling point of water at the elevation of Colorado springs is almost 10 degrees cooler than it is at sea level.

Adding a return line allows excess fuel that is not needed to keep the carburetor filled to be cycled back to the fuel tank and will actually allow THAT fuel to vaporize first and actually help cool the pump down a lot. I would personally recommend putting in a three port pump and run the return line back to the tank first. You will likely not have another issue with it. I have a three port pump and have run my truck through the cascades at 3-5,000ft elevation and near 100 degrees with no issue. I had a 74 C20 for a while that would have the same symptoms you are having on hot days. It did not have a return line and I'm pretty sure it was vapor locking when I would get it on the freeway.

@Bextreme04 is there an option for the return line into the tank other than ordering a new sending unit? I ask because I can switch out the fuel pump and add a return line here in the mountains... but can order and replace a new sending unit here.

Thoughts?

 

[Bextreme04]

@Bextreme04 is there an option for the return line into the tank other than ordering a new sending unit? I ask because I can switch out the fuel pump and add a return line here in the mountains... but can order and replace a new sending unit here.

Thoughts?

Well, you've had it out twice now... is there another port available for the return line? You need at least one external vent. In general, the gas cap will not be vented. If you only have a three port sender, then you have a feed, a vent, and a tank filler vent tube. The tank filler vent tube goes into the filler neck and does not allow for venting of the tank.

 

[Bextreme04]

Quick question: my oem sending unit has three ports:
- a supply tube to the fuel pump
- a vent tube up to the gas cap
- a vent that has basically a dust cover on it.

Can I connect a return line to either of the vent tubes or are the internally ’one-way’ vents?

In other words, can I use my existing sending unit to add a return line or must I upgrade to a 4 port sending unit?

I would recommend the update to the 4-port as the correct solution. In the mountains, in a pinch, I would recommend you get a y-pipe and splice the pump return into the larger filler vent line. Leave the tank vent with the check valve on it untouched or you will get pressure or vacuum built up in the tank and you'll have even more fuel starvation or potentially a tank rupture.

I would not keep this as a permanent solution, but it should work fine temporarily.

 

[WFO]

I changed the mechanical pump on this Blazer in the parking lot of Oreilly’s in Pueblo… the only real pain was keeping the pump rod up to slide in the pump lever…

If you'll put some grease around the pump rod it will stay up there.

 

[7900_Blazer]

If you'll put some grease around the pump rod it will stay up there.

Ah, of course, great trick.

 

[SirRobyn0]

Thank you for the detailed responses.

Your welcome I hope it helps.

I think my first upgrade will be adding a return line. The only question I have is what is best option for adding a return to the tank.

The best thing would be to replace the sending unit assembly with a 4 port sending unit, you'd also get a new sending unit for the gauge, pick up tube, sock and seal with that.

 

[QBuff02]

the only real pain was keeping the pump rod up to slide in the pump lever…

on a lot of Chevrolet engines if you look down at the passenger side front of the block next to the timing cover, there is a bolt (two bolt holes on top of each other, early motor mount locations) that lines up with the location of the fuel pump push rod in the block but it is a short bolt for normal operation to keep interference from happening. If you remove the fuel pump and push your finger against the fuel pump push rod, have someone bump the engine over until you feel its all the way bottomed out against the base of the pump drive cam lobe, remove the above mentioned bolt, install a longer one until it is snug (basically finger tight) so it holds the pump push rod, install your new gasket and fuel pump then remove the longer bolt and install the original bolt back in it's location and that's how you change a fuel pump on Chevrolet engines without headache. Grease is a good trick too, and usually the much faster method! because not all blocks had the provision, but the above is the proper way and most people don't know that little nugget of installation information even exists.

 

[Raider L]

Buy a Holley! Problem solved!!

 

[Raider L]

I've had a brand new Holley fuel pump fail not long after I replaced it. I contacted Holley and they sent me a new one free of charge. But I had already bought a Jegs pump and that's what's on the truck now and has been for years. That's why I'm gauged out. I have a "fuel Pressure" gauge right next to the fuel level on the dash so if the pump craps out I'll see no pressure on the gauge. And if I'm trying to start the engine and I see no pressure I'll know it's the pump. I also have a fuel pressure gauge on the "Y" block with the line coming up from the pump and a line coming from the "Y" block to the filter and on to the carb. If I open the hood due to a no start the first thing I look at is that pressure gauge. And yeah, my pump is the kind that returns fuel to the tank. If you sit there long enough you can see the pressure gauge drop to almost zero, but it takes awhile.

This is the most perplexing problem I think I've ever heard of. But I'm starting to think that there is something in the sending unit that at times won't allow fuel to move. And the gas in the 5 gal. bucket mostly proves it.
The tank is clean,
you've replaced every hose there is going and coming from the tank,
and I agree the might be a problem with the fuel pump, but if it is it's a new problem adding to the overall situation. If you have a good pump put it on so that saves having to buy another one, just to see. And I understand that all these changes require you having to drive around all over the place just to end up back to square one.
BUT, I think you've isolated the problem with the 5 gal. bucket, it runs when you bypass the sending unit.

 

[Raider L]

@QBuff02,

That's right, that bolt down there. I mentioned to someone here about that bolt to. I forget what the one above it is for. But I keep my long one in the bolt above the short one so all I have to do is change them out to hold the rod. I don't even bump the motor over, I put the long bolt in just to hold what I've got. I usually have to work alone so I don't have that help when I need it.

 

[78C10BigTen]

I changed the mechanical pump on this Blazer in the parking lot of Oreilly’s in Pueblo… the only real pain was keeping the pump rod up to slide in the pump lever…

There should be a bolt hole in the front of the block, push the rod up' screw bolt in against it and pop the pump on. Afterwards pull that bolt back out to drop the push rod.